Application of high EPA-producing Mortierella alpina in laying hen feed for egg DHA accumulation

Polyunsaturated fatty acids (PUFAs), especially eicosapentaenoic acid (EPA, C20:5) and docosahexaenoic acid (DHA, C22:6), are beneficial for human health. In this study, we selected a high EPA content (30% in total fatty acids) strain of Mortierella alpina CCFM 698 that overexpressed an ω-3 fatty acid desaturase from Phytophthora parasitica, and investigated the cell growth and lipid accumulation of this strain in a 65 L airlift fermenter with glucose batch feeding. The maximum cell dry weight was 28.7 g L^-1 and the highest total fatty acid content was 33.0% (w/w) in cell dry weight. The highest EPA yield was 1.8 g L^-1. Both low and high dose supplementation of this strain into the feed of laying hens increased DHA accumulation in the yolk. The highest DHA content of 7.61 mg g^-1 yolk was achieved in Fengda-1 laying hens with 4% supplementation and the DHA production per egg was 118.46 mg. However, Hy-Line Brown laying hens displayed a higher DHA production per egg and the value was 131.50, 131.72, 131.95 mg with 1.5%, 2%, 4% supplementation, respectively. The lowest ratio of ω-6/ω-3 PUFAs (3.53) was obtained in Hy-Line Brown laying hens with 4% supplementation. These results suggest that M. alpina CCFM 698 can be used as an alternative source of ω-3 PUFAs in feed to produce nutritious eggs with high DHA content.